1. Field of the Invention
The present invention relates to apparatus and methods for repair of weakened tissue in medical and veterinary procedures, such as in weakened heart mitral and tricuspid valve repairs.
2. Description of Related Art
Several accepted procedures exist for reinforcing weakened tissue in medical and veterinary procedures. One area which has received considerable attention in this regard is the repair of mitral and tricuspid heart valves.
As is known, the functioning and effectiveness of human and animal heart valves can be compromised through functional and/or organic causes. If the valve becomes weakened, regurgitation of blood can occur around the valve's leaflets, reducing the heart's effectiveness in pumping blood. While prosthetic devices exist to replace these valves, none is considered fully acceptable. Accordingly, whenever practicable it is accepted practice today to perform conservative surgical procedures to preserve a patient's native valve.
One of the simplest procedures in this regard was developed by Dr. Norberto G. De Vega in the early 1970s ("De Vega"). In this procedure, one or more seams are created within tissue along the periphery of a weakened section of heart valve using conventional suture material. Once the seam is in place, the tissue is simply cinched along the suture in a "purse string" manner. The suture is knotted off at each end, often with the use of pledgets to prevent tearing, to retain the tissue in a plicated orientation. This procedure serves to reduce the size of the valve opening and to improve the valve's efficiency.
Among the advantages of the De Vega procedure are that it is relatively effective at correcting many tricuspid and mitral valve deficiencies, it can be performed rapidly (usually on the order of about 10 minutes), it generally requires little specialized equipment and has a relatively short learning curve, and it generally introduces minimal foreign material within the heart so as to reduce the risk of thrombus generation.
While the De Vega technique has proven to be effective, it continues to be plagued with some serious drawbacks. One serious problem repeatedly observed with the De Vega procedure is that the sutures employed can pull out of the tissue and "guitar string" across the valve annulus. This event not only destroys the repair but also presents an undesirable Obstruction across the valve opening. In one response to this concern, it has been suggested that the sutures should be buried within the atrial endocardium to provide better reinforcement of the suture. Unfortunately this procedure is believed to provide only limited improvement and may result in even more extensive damage in the case of a pull out.
Another suggested correction is the use of pledgets at each stitch in the annulus to reinforce the sutures. While this procedure may solve the tearing problem, it eliminates many of the other advantages of the De Vega procedure, such as the minimizing of foreign material, the speed and ease of the surgery, and the ability to remove the sutures rapidly in the event of the need for further repair or heart valve replacement.
Another common complaint with the De Vega procedure is that the bunching of tissue around the periphery of the valve through the purse string procedure necessarily distorts the valve opening from its natural shape and thus limits improvement in valve function. This problem is particularly compounded where a large segment of the valve is repaired in this manner or where surgeons inexperienced with this technique provide too little or too much plication to the tissue.
Another procedure which has addressed many of the drawbacks of the De Vega technique was developed by Dr. Alain Carpentier in the late 1960s ("Carpentier"). In this procedure a series of different sized fabric coated stainless steel or titanium rings are provided in the approximate original shape of the valves to be repaired. The surgeon first sizes the valve with a sizing template to select the correct size of ring. Next a large number of sutures are sewn in place to create a circle of guide lines around the periphery of the valve annulus. By attaching each of the guide lines to the ring, the ring can be positioned down the guide lines to draw the valve opening into its approximate original shape. Each of the guidelines is then tied off to retain the ring around the annulus.
This technique has been shown to provide significantly improved valve function, but has many critical problems. First, the entire procedure is complicated, requires ancillary equipment, and demands advanced surgical techniques. Moreover, the need to establish and maintain many guide lines through this procedure vastly increases the amount of time needed to perform this repair (generally requiring 30 minutes or more). As a result, due to time constraints it is often impractical to perform a Carpentier repair when this operation is ancillary to other open heart procedures. Other problems with the Carpentier operation include: the risk of off-site impact from the procedure, such as possible surgical damage to the atrioventricular (AV) bundle; the large amount of foreign material exposed to flowing blood, increasing the risk of thrombus generation; and the rigidness of the ring limiting the possible placement and use of this procedure, with particular concern over possibly impeding other heart function, such as distortion of proper systolic motion of the annulus in a mitral valve repair.
The problem of the rigidness of the ring limiting its placement or distorting other heart functions has been addressed through a number of further advances. One device developed by Dr. Carlos M. G. Duran employs a flexible ring, such as one constructed from a flexible polyester polymer, which is mounted in a manner similar to that employed by the Carpentier procedure ("Duran"). Unfortunately, this ring continues to have many of the other drawbacks of the Carpentier ring. Additionally, the flexible ring cannot provide the amount of support possible with a rigid ring, thus decreasing or eliminating one of the chief benefits of the Carpentier device-the restoration and maintenance of the original valve shape.
Another flexible prosthesis is the "flexible linear reducer" developed by Dr. Bex of France. In this device, a silicone bead with embedded polyester fibers is sutured around a distended annulus from one commissure of the affected valve to the other. Unfortunately, this device has many of the same deficiencies as the flexible Duran ring.
Dr. Carpentier has likewise acknowledged some of the deficiencies of his original concept and has developed a number of modifications. Among these are rings which are only semi-rigid, and rings with cut-outs or other modified shapes to avoid affecting other areas of the heart. Again, however, these improved devices still retain many of the same deficiencies discussed above, including excessive installation times and unduly complicated installation procedures.
In light of the foregoing, it is a primary purpose of the present invention to provide an improved apparatus and method of use for reinforcing weakened tissue that can be installed quickly and relatively easily.
It is a further purpose of the present invention to provide such an apparatus and method of use that is resistant to pull-out from anchoring tissue.
It is another purpose of the present invention to provide such an apparatus and method of use that provides an effective repair to cardiac valves by reinforcing the area around the valve's leaflets.
It is still another purpose of the present invention to provide such an apparatus and method that subjects a patient to minimal side effects, such as risk of off-site organ damage or function impediment, or excessively increased risk of thrombosis.
It is yet another purpose of the present invention to provide such an apparatus and method that requires minimal specialized equipment to perform and which can be effectively practiced with a relatively short training curve.
These and other purposes of the present invention will become evident from review of the following specification.